U.S. patent number 10,563,109 [Application Number 15/300,649] was granted by the patent office on 2020-02-18 for additive for slurry, drilling mud, and cement slurry.
This patent grant is currently assigned to KURARAY CO., LTD.. The grantee listed for this patent is KURARAY CO., LTD.. Invention is credited to Yosuke Kumaki, Yasutomo Saito.
United States Patent |
10,563,109 |
Kumaki , et al. |
February 18, 2020 |
Additive for slurry, drilling mud, and cement slurry
Abstract
Provided by the present invention is an additive for a slurry
being capable of inhibiting viscosity elevation and dehydration at
high temperatures at low cost, through use for a slurry for civil
engineering and construction (for example, a drilling mud and a
drilling cement slurry for use in well drilling. etc.), and the
like. A powdery additive for a slurry, the powdery additive
containing a vinyl alcohol polymer, which has: a solubility of 25%
or less when immersed in hot water at 60.degree. C. for 3 hours; a
degree of saponification of at least 99.5 mol %; an average degree
of polymerization of at least 1,500 and 4,500 or less; and the
amount of 1,2-glycol linkage of 1.8 mol % or less, the powdery
additive being capable of passing through a sieve having a nominal
mesh opening size of 1.00 mm.
Inventors: |
Kumaki; Yosuke (Kurashiki,
JP), Saito; Yasutomo (Kurashiki, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
KURARAY CO., LTD. |
Kurashiki-shi |
N/A |
JP |
|
|
Assignee: |
KURARAY CO., LTD.
(Kurashiki-shi, JP)
|
Family
ID: |
54240237 |
Appl.
No.: |
15/300,649 |
Filed: |
March 23, 2015 |
PCT
Filed: |
March 23, 2015 |
PCT No.: |
PCT/JP2015/058799 |
371(c)(1),(2),(4) Date: |
September 29, 2016 |
PCT
Pub. No.: |
WO2015/151910 |
PCT
Pub. Date: |
October 08, 2015 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20170174971 A1 |
Jun 22, 2017 |
|
Foreign Application Priority Data
|
|
|
|
|
Mar 31, 2014 [JP] |
|
|
2014-074291 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C04B
40/0042 (20130101); C04B 28/02 (20130101); C09K
8/5083 (20130101); C09K 8/467 (20130101); C09K
8/487 (20130101); C08F 216/06 (20130101); C09K
8/035 (20130101); C04B 16/04 (20130101); C04B
28/02 (20130101); C04B 24/02 (20130101); C04B
24/2623 (20130101); C04B 40/0042 (20130101); C04B
24/02 (20130101); C04B 24/2623 (20130101); C04B
2103/46 (20130101); C04B 2201/10 (20130101); C04B
2111/70 (20130101); C04B 2103/0057 (20130101) |
Current International
Class: |
C09K
8/035 (20060101); C04B 16/04 (20060101); C09K
8/467 (20060101); C04B 40/00 (20060101); C08F
216/06 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1495205 |
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May 2004 |
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CN |
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101466811 |
|
Jun 2009 |
|
CN |
|
101484547 |
|
Jul 2009 |
|
CN |
|
102822266 |
|
Dec 2012 |
|
CN |
|
103124748 |
|
May 2013 |
|
CN |
|
2004-344751 |
|
Dec 2004 |
|
JP |
|
2009-221461 |
|
Oct 2009 |
|
JP |
|
2 204 012 |
|
May 2003 |
|
RU |
|
2 266 312 |
|
Dec 2005 |
|
RU |
|
2 388 782 |
|
May 2010 |
|
RU |
|
717070 |
|
Feb 1980 |
|
SU |
|
2012/043280 |
|
Apr 2012 |
|
WO |
|
Other References
International Search Report dated Jun. 23, 2015, in PCT/JP15/58799
filed Mar. 23, 2015. cited by applicant .
J. Plank, et al., "Comparative Study of the Working Mechanisms of
Chemically Different Cement Fluid Loss Polymers,", Society of
Petroleum Engineers Conference Paper ID 121542, 2009, 26 pages.
cited by applicant .
Office Action dated Nov. 16, 2018 in Russian Patent Application No.
2016142352, 13 pages (with English translation). cited by
applicant.
|
Primary Examiner: Wu; Jenny R
Attorney, Agent or Firm: Oblon, McClelland, Maier &
Neustadt, L.L.P.
Claims
The invention claimed is:
1. A powdery additive comprising a vinyl alcohol polymer, wherein
the vinyl alcohol polymer has: a solubility of 25% or less when
immersed in hot water at 60.degree. C. for 3 hours; a degree of
saponification of at least 99.5 mol %; an average degree of
polymerization of 1,500 to 4,500; and an amount of 1,2-glycol
linkage of 1.8 mol % or less, and the powdery additive is capable
of passing through a sieve having a nominal mesh opening size of
1.00 mm, wherein the solubility is represented by the following
formula: solubility=(4 g weight of vinyl alcohol polymer powder
charged into 100 g of the hot water-weight of undissolved vinyl
alcohol polymer powder separated by using a wire mesh having a
nominal mesh opening size of 75 micron measured after drying with a
heating dryer at 105.degree. C. for 3 hours)/(4 g weight of vinyl
alcohol polymer powder charged into 100 g of the hot water),
wherein a proportion of an ethylene unit with respect to total
structural units in the vinyl alcohol polymer is less than 10 mol
%.
2. The powdery additive according to claim 1, which is suitable as
an additive for a slurry for civil engineering and
construction.
3. The powdery additive according to claim 2, is suitable as an
additive for a drilling mud.
4. The powdery additive according to claim 1, which is capable of
passing through a sieve having a nominal mesh opening size of 500
um.
5. The powdery additive according to claim 2, is suitable as an
additive for a cement slurry.
6. The powdery additive according to claim 1, which is capable of
passing through a sieve having a nominal mesh opening size of 250
um.
7. A drilling mud comprising the powdery additive according to
claim 1.
8. A method of producing a drilling mud, comprising mixing: the
powdery additive according to claim 1; water; and a muddy
material.
9. A cement slurry comprising the powdery additive according to
claim 1.
10. A method of producing a cement slurry, comprising mixing: the
powdery additive according to claim 1; a liquid; and a hardening
powder.
Description
TECHNICAL FIELD
The present invention relates to an additive for a slurry, a
drilling mud and a cement slurry, and a production method of a
drilling mud and a production method of a cement slurry.
BACKGROUND ART
In wells and the like for collecting buried resources such as
petroleum and natural gases, a slurry for civil engineering and
construction typified by a drilling mud and a drilling cement
slurry has been conventionally used.
The drilling mud plays roles in, for example: transporting drilled
clasts, drilling wastes and the like; improving lubricating
properties of bits and drill pipes; filling in holes on the porous
ground; balancing out the reservoir pressure that results from the
hydrostatic pressure (pressure from the rock stratum); and the
like. In general, the drilling mud contains water and bentonite as
principal components to which barites, salts, clays and the like
are further added, whereby intended performances can be achieved.
Such a drilling mud is demanded to have appropriate flow
characteristics such as having temperature stability, not being
significantly affected by variation of concentrations of
electrolytes (for example, carboxylic acid salts) in the ground,
and the like. To meet such demands, adjusting the viscosity of the
drilling mud, and inhibiting dissipation of the moisture contained
in the drilling mud (hereinafter, may be also referred to as
"dehydration") may be required. For adjusting the viscosity of the
drilling mud and for inhibiting the dehydration, a method which
includes adding a polymer, for example, starch, a starch ether
(carboxymethyl starch, etc.), carboxymethyl cellulose,
carboxymethyl hydroxyethyl cellulose or the like is usually
adopted.
However, the addition of such polymers may extremely elevate the
viscosity of the drilling mud, whereby injection of the drilling
mud by a pump may be difficult. Moreover, there may exist
disadvantages that dehydration of starches and derivatives thereof
may not be sufficiently inhibited within a temperature range
exceeding about 120.degree. C., and the dehydration may not be
sufficiently inhibited by carboxymethyl cellulose and carboxymethyl
hydroxyethyl cellulose within a temperature range of 140.degree. C.
to 150.degree. C.
On the other hand, the drilling cement slurry is used for, e.g.,
fixing the casing pipe in the well and protecting the inside wall
of the well through cementing which comprises injecting the
drilling cement slurry into tubular void portions between the
stratum and a casing pipe installed in the well, followed by
hardening therein. In general, the injection of the drilling cement
slurry into tubular void portions is carried out by using a pump.
Thus, the drilling cement slurry is required to have extremely low
viscosity and not to be accompanied by segregation such that the
injection thereof by using the pump can be readily carried out.
However, in cementing a well, a defect is likely to occur in a
cemented part due to: material segregation; dissipation of the
moisture to cracks in the well; and the like. Accordingly, a
dehydration-reducing agent such as walnut shells, cotton seeds,
clay minerals, polymer compounds and the like has been employed to
be added to the drilling cement slurry, and in particular, vinyl
alcohol polymers being a polymer compound are a well-known
dehydration-reducing agent.
In regard to the vinyl alcohol polymer as a dehydration-reducing
agent, for example, Patent Document 1 discloses a method in which a
vinyl alcohol polymer having a degree of saponification of at least
95 mol % is used; Patent Document 2 discloses a method in which a
vinyl alcohol polymer having a degree of saponification of 92 mol %
or less is used; and Patent Document 3 discloses a method in which
a vinyl alcohol polymer having a degree of saponification of at
least 99 mol % is used. However, according to these methods,
performances of the dehydration-reducing agent at high temperatures
in particular, may be insufficient, or feeding of the drilling
cement slurry by the pump may be difficult through elevating the
viscosity.
In order to moderate the viscosity elevation of the drilling cement
slurry and/or to improve deteriorated performances of the
dehydration-reducing agent at high temperatures: Patent Document 4
discloses a method in which a vinyl alcohol polymer crosslinked by
melamine-formaldehyde is used; Patent Document 5 discloses a method
in which a vinyl alcohol polymer produced by crosslinking of
hydroxyl groups of a vinyl alcohol polymer by an acetalization
reaction or the like is used; and Patent Document 6 discloses a
method in which a vinyl alcohol polymer produced by pH-sensitive
crosslinking using a boron ion, etc., is used. Although a given
effect of improving the performances of the dehydration-reducing
agent at high temperatures is achieved according to these methods,
it is necessary to carry out the reaction with the crosslinking
agent after a water soluble vinyl alcohol polymer is produced
beforehand, and thus the cost is likely to be increased.
PRIOR ART DOCUMENTS
Patent Documents
Patent Document 1: U.S. Pat. No. 4,569,395 Patent Document 2: U.S.
Pat. No. 4,967,839 Patent Document 3: U.S. Pat. No. 7,731,793
Patent Document 4: U.S. Pat. No. 5,061,387 Patent Document 5: U.S.
Pat. No. 6,656,266 Patent Document 6: U.S. Pat. No. 6,739,806
Nonpatent Documents
Nonpatent Document 1: Society of Petroleum Engineers Conference
Paper ID 121542
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
An objective of the present invention is to provide an additive for
a slurry being capable of inhibiting in a slurry such as a slurry
for civil engineering and construction (for example, a drilling mud
and a drilling cement slurry for use in well drilling and the
like), dehydration from the slurry and viscosity elevation of the
slurry at high temperatures at low cost. Furthermore, another
objective of the present invention is to provide a drilling mud and
a drilling cement slurry containing the additive for a slurry, and
a production method of the drilling mud and a production method of
the drilling cement slurry.
Means for Solving the Problems
The present inventors thoroughly studied in order to achieve the
objectives described above, and consequently found that when a
vinyl alcohol polymer having: a solubility of 25% or less when
immersed in hot water at 60.degree. C. for 3 hrs; a degree of
saponification of at least 99.5 mol %; an average degree of
polymerization of at least 1,500 and 4,500 or less; and an amount
of 1,2-glycol linkage of 1.8 mol % or less is used, and a powdery
form being capable of passing through a sieve having a nominal mesh
opening size of 1.00 mm is adopted, a slurry can be readily
obtained in which viscosity elevation and dehydration at high
temperatures are inhibited. Thus, as a result of further
investigations based on these findings, the present invention was
accomplished.
More specifically, an aspect of the present invention is directed
to a powdery additive for a slurry, the powdery additive containing
a vinyl alcohol polymer, in which the vinyl alcohol polymer has: a
solubility of 25% or less when immersed in hot water at 60.degree.
C. for 3 hrs; a degree of saponification of at least 99.5 mol %; an
average degree of polymerization of at least 1,500 and 4,500 or
less; and an amount of 1,2-glycol linkage of 1.8 mol % or less, and
the powdery additive is capable of passing through a sieve having a
nominal mesh opening size of 1.00 mm.
The proportion of ethylene unit with respect to the total
structural units in the vinyl alcohol polymer is preferably less
than 10 mol %.
The additive for a slurry can be preferably used as an additive for
a slurry used in civil engineering and construction. The additive
for a slurry used in civil engineering and construction can be more
preferably used as an additive for a drilling mud (an additive for
a drilling mud slurry), or an additive for a cement slurry.
When the additive for a slurry is the additive for a drilling mud,
the additive is preferably capable of passing through a sieve
having a nominal mesh opening size of 500 .mu.m.
When the additive for a slurry is the additive for a cement slurry,
the vinyl alcohol polymer is preferably capable of passing through
a sieve having a nominal mesh opening size of 250 .mu.m.
Still another aspects of the present invention include: a drilling
mud containing the additive for a slurry as an additive for a
drilling mud; and a production method of a drilling mud including
the step of mixing the additive for a drilling mud, water, and a
muddy material.
Yet another aspects of the present invention include: a cement
slurry containing the additive for a slurry as an additive for a
cement slurry; and a production method of a cement slurry including
the step of mixing the additive for a cement slurry, a hardening
powder, and a liquid.
As referred to hereinabove, the "nominal mesh opening size" means
the nominal mesh opening size defined in JIS-Z8801: 2000 "Test
sieves--Part 1: Test sieves of metal wire cloth". The same applies
to the "nominal mesh opening size" described in the following.
Effects of the Invention
According to the aspects of the present invention, the additive for
a slurry, the drilling mud and the drilling cement slurry being
capable of inhibiting viscosity elevation and dehydration at high
temperatures at low cost, in slurries such as a slurry for civil
engineering and construction (for example, drilling muds and
drilling cement slurries for use in well drilling and the like) are
provided.
DESCRIPTION OF EMBODIMENTS
Embodiments of the present invention include: an additive for a
slurry, a drilling mud and a production method thereof, and a
cement slurry and a production method thereof. Hereinafter, the
embodiments of the present invention will be described in
detail.
Additive for Slurry
The additive for a slurry according to an embodiment of the present
invention is to be added to a slurry for civil engineering and
construction, etc., and is suitably added to a drilling mud and a
cement slurry. Of course, the additive for a slurry may be used not
only in the drilling mud and the cement slurry, but also in
slurries for other intended usage which require inhibition of
viscosity elevation and dehydration at high temperatures.
The additive for a slurry contains a vinyl alcohol polymer
(hereinafter, may be also referred to as "PVA"), and has a powdery
form being capable of passing through a sieve having a nominal mesh
opening size of 1.00 mm. The PVA is contained in the additive for a
slurry in a powdery form (hereinafter, such a powdery PVA may be
also referred to as "PVA powder"). The additive for a slurry may
contain only the PVA powder, or may contain optional component(s)
in addition to the PVA powder. The lower limit of the percentage
content of the PVA powder in the additive for a slurry is, for
example, 50% by mass, and preferably 80% by mass. On the other
hand, the upper limit of the percentage content of the PVA powder
in the additive for a slurry is typically 100% by mass.
Particle Size
The PVA powder has a particle size that enables passage through a
sieve having a nominal mesh opening size of 1.00 mm (16 mesh). When
such a PVA powder is contained as an additive in a drilling mud, a
drilling cement slurry or the like, inhibition of dehydration from
the slurry at high temperatures is facilitated. On the other hand,
the lower limit value of the particle size of the PVA powder falls
within the range not leading to extremely great solubility, and the
particle size typically does not enable passage through a sieve
having a nominal mesh opening size of 45 .mu.m (325 mesh), and the
particle size preferably does not enable passage through a sieve
having a nominal mesh opening size of 53 .mu.m (280 mesh).
Solubility
The lower limit of the solubility of the PVA powder when immersed
in hot water at 60.degree. C. for 3 hrs is preferably 5%, more
preferably 10%, and still more preferably 15%. On the other hand,
the upper limit of the solubility is 25%, preferably 22%, and more
preferably 18%. When the solubility of the PVA powder is greater
than 25%, the dehydration from the slurry at high temperatures can
not be sufficiently inhibited.
In this regard, the solubility of the PVA powder may be determined
by: adding 4 g of the PVA powder in 100 g of water heated to
60.degree. C.; stirring the mixture for 3 hrs with a magnetic
stirrer; and calculating from the weight of the initially charged
PVA powder (4 g), and the weight of undissolved PVA powder
separated by using a wire mesh having a nominal mesh opening size
of 75 .mu.m (200 mesh) measured after drying with a heating dryer
at 105.degree. C. for 3 hrs.
Vinyl Alcohol Polymer (PVA)
PVA is synthesized by saponifying a vinyl ester polymer obtained by
polymerizing a vinyl ester monomer. In other words, the PVA
contained in the additive for a slurry can be easily synthesized by
a well-known method so as to have intended characteristics, without
purposely carrying out crosslinking and the like; therefore, the
production cost of the additive for a slurry can be lowered.
As the polymerization procedure of the vinyl ester monomer, for
example, bulk polymerization, solution polymerization, suspension
polymerization, emulsion polymerization, dispersion polymerization
and the like may be exemplified, and in light of an industrial
viewpoint, the solution polymerization, the emulsion polymerization
and the dispersion polymerization are preferred. The polymerization
system of the vinyl ester monomer may be any of batch
polymerization, semi-batch polymerization and continuous
polymerization.
Examples of the vinyl ester monomer include vinyl acetate, vinyl
formate, vinyl propionate, vinyl caprylate, vinyl versatate and the
like, and of these, vinyl acetate is preferred in light of an
industrial viewpoint.
PVA may be a product of saponification of a vinyl ester polymer
obtained by copolymerizing ethylene. By copolymerizing a vinyl
ester with ethylene, the solubility of the PVA after the
saponification can be decreased. Accordingly, the viscosity
elevation of the slurry and the dehydration at high temperatures
can be more inhibited.
The PVA may also be a product of saponification of a vinyl ester
polymer obtained by copolymerizing other monomer except for the
vinyl ester monomer and ethylene, within the range not impairing
principles of the present invention. Examples of the other monomer
include: .alpha.-olefins such as propylene, n-butene and
isobutylene; acrylic acid and salts thereof; acrylic acid esters
such as methyl acrylate, ethyl acrylate, n-propyl acrylate,
i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl
acrylate, 2-ethylhexyl acrylate, dodecyl acrylate and octadecyl
acrylate; methacrylic acid and salts thereof; methacrylic acid
esters such as methyl methacrylate, ethyl methacrylate, n-propyl
methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl
methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate,
dodecyl methacrylate and octadecyl methacrylate; acrylamide;
acrylamide derivatives such as N-methylacrylamide,
N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide,
acrylamidopropanesulfonic acid and salts thereof,
acrylamidopropyldimethylamine and salts thereof or quaternary salts
of the same, and N-methylolacrylamide and derivatives thereof;
methacrylamide; methacrylamide derivatives such as
N-methylmethacrylamide, N-ethylmethacrylamide,
methacrylamidopropanesulfonic acid and salts thereof,
methacrylamidopropyldimethylamine and salts thereof or quaternary
salts of the same, and N-methylolmethacrylamide and derivatives
thereof; vinyl ethers such as methyl vinyl ether, ethyl vinyl
ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl
ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl
ether and stearyl vinyl ether; nitriles such as acrylonitrile and
methacrylonitrile; halogenated vinyls such as vinyl chloride and
vinyl fluoride; halogenated vinylidenes such as vinylidene chloride
and vinylidene fluoride; allyl compounds such as allyl acetate and
allyl chloride; unsaturated dicarboxylic acids such as maleic acid,
itaconic acid and fumaric acid, and salt thereof or esters of the
same; vinylsilyl compounds such as vinyltrimethoxysilane;
isopropenyl acetate; and the like.
In the polymerization of the vinyl ester monomer, a chain transfer
agent may coexist for the purpose of regulating the average degree
of polymerization of the PVA, and the like. Examples of the chain
transfer agent include: aldehydes such as acetaldehyde,
propionaldehyde, butyraldehyde and benzaldehyde; ketones such as
acetone, methyl ethyl ketone, hexanone and cyclohexanone;
mercaptans such as 2-hydroxyethanethiol; thiocarboxylic acids such
as thioacetic acid; halogenated hydrocarbons such as
trichloroethylene and perchloroethylene; and the like. Of these,
the aldehydes and the ketones are preferred. The amount of the
chain transfer agent added may be predetermined depending on the
chain transfer constant of the added chain transfer agent, and the
average degree of polymerization to be achieved for the PVA, and
the like.
As the saponification reaction of the vinyl ester polymer, a
well-known alcoholysis or hydrolysis reaction may be adopted in
which a basic catalyst such as sodium hydroxide, potassium
hydroxide or sodium methoxide, or an acidic catalyst such as
p-toluenesulfonic acid is used.
Examples of the solvent which may be used in the saponification
reaction include: alcohols such as methanol and ethanol; esters
such as methyl acetate and ethyl acetate; ketones such as acetone
and methyl ethyl ketone; aromatic hydrocarbons such as benzene and
toluene; and the like. These solvents may be used either alone of
one type, or in combination of two or more thereof. Of these,
carrying out the saponification reaction by using as the solvent
methanol or a mixed solution of methanol with methyl acetate, in
the presence of sodium hydroxide as the basic catalyst is preferred
due to convenience.
Degree of Saponification
The lower limit of the degree of saponification of the PVA is 99.5
mol %, preferably 99.7 mol %, more preferably 99.8%, and
particularly preferably 99.9 mol %. The PVA is a crystalline
polymer having a crystalline part moiety that results from a
hydrogen bond of the hydroxyl group included. The degree of
crystallinity of the PVA is increased as the degree of
saponification increases. Also, the increased degree of
crystallinity leads to a decrease in water solubility of the PVA.
In particular, the PVA exhibits significant alteration of the
solubility in water at high temperatures with a borderline of the
degree of saponification of 99.5 mol %. Thus, the PVA having the
degree of saponification of at least 99.5 mol % has superior water
resistance (having low solubility) due to the strength of the
hydrogen bond, and may have water resistance that is comparable to
PVAs having chemical crosslinking. Therefore, when the PVA has the
degree of saponification of at least 99.5 mol %, even if the PVA is
not subjected to chemical crosslinking, the viscosity elevation and
the dehydration at high temperatures of the slurry can be
inhibited, and consequently the cost can be lowered as the chemical
crosslinking step can be omitted. On the other hand, when the
degree of saponification is less than the lower limit, dehydration
at high temperature may not be sufficiently inhibited in the case
of use as the additive for a slurry. It is to be noted that the
degree of saponification of the PVA is a value determined according
to JIS-K6726: 1994.
Average Degree of Polymerization
The lower limit of the average degree of polymerization of the PVA
is 1,500, preferably 1,700, more preferably 1,800, and still more
preferably 2,000. On the other hand, the upper limit of the average
degree of polymerization is 4,500, preferably 4,250, more
preferably 4,000, and still more preferably 3,800. When the average
degree of polymerization of the PVA is less than the lower limit,
the dehydration of the slurry at high temperatures may not be
sufficiently inhibited which may result from an increase in the
solubility to some extent. Whereas, when the average degree of
polymerization is greater than the upper limit, the production of
the PVA becomes difficult, and the viscosity of the slurry at high
temperatures may be excessively increased.
As referred to herein, the average degree of polymerization of the
PVA is a value determined according to JIS-K6726: 1994. More
specifically, the average degree of polymerization of the PVA can
be determined from a limiting viscosity [.eta.] (dL/g) measured in
water at 30.degree. C. according to the following formula: average
degree of
polymerization=([.eta.].times.1000/8.29).sup.(1/0.62).
Amount of 1,2-Glycol Linkage
The lower limit of the amount of the 1,2-glycol linkage of the PVA
is 0.5 mol %, and more preferably 1.0 mol %. On the other hand, the
upper limit of the amount of the 1,2-glycol linkage of the PVA is
1.8 mol %, preferably 1.7 mol %, and more preferably 1.6 mol %.
When the amount of the 1,2-glycol linkage of the PVA is thus 1.8
mol % or less, crystallization of the PVA is hardly inhibited by
the 1,2-glycol linkage, and therefore the degree of crystallinity
of the PVA is likely to be increased, whereby the solubility of the
PVA is consequently decreased. Such PVA having a comparably smaller
amount of 1,2-glycol linkage is preferably obtained by polymerizing
the vinyl ester monomer under a condition of the temperature lower
than usual.
As referred to herein, the amount of the 1,2-glycol linkage of the
PVA may be determined from the peaks in the NMR spectrum. After
being saponified to the degree of saponification of at least 99.9
mol %, the PVA sufficiently washed with methanol and then dried
under reduced pressure at 90.degree. C. for 2 days is dissolved in
DMSO-D6, to which several drops of trifluoroacetic acid are added.
Thus obtained sample is subjected to the measurement at 80.degree.
C. by using proton NMR ("GX-500" available from JEOL Ltd.) at 500
MHz. The peaks derived from methine of the vinyl alcohol unit
correspond to 3.2 ppm to 4.0 ppm (integrated value: A'), whereas
the peak derived from one methine of the 1,2-glycol linkage
corresponds to 3.25 ppm (integrated value: B'), and thus the amount
of 1,2-glycol linkage can be calculated according to the following
formula: Amount of 1,2-glycol linkage (mol %)=B'(100-.DELTA.)/A'
wherein, ".DELTA." denotes the ethylene modification amount (mol
%).
The amount of 1,2-glycol linkage of the vinyl alcohol polymer may
be adjusted by the copolymerization of a monomer typified by, for
example, ethylene carbonate as well as the polymerization
temperature and the like.
Proportion of Ethylene Unit
The proportion of the ethylene unit in the PVA is, with respect to
the total structural units in the PVA, preferably less than 10 mol
%, more preferably less than 9 mol %, and particularly preferably
less than 8 mol %. When the proportion of the ethylene unit is 10
mol % or greater, obtaining the PVA having the average degree of
polymerization of at least 1,500 may be difficult.
As referred to herein, the proportion of the ethylene unit in the
PVA is a value determined from proton NMR of the vinyl ester
polymer that is a precursor of the PVA. More specifically, after
the vinyl ester polymer as the precursor is sufficiently purified
by reprecipitation with n-hexane/acetone at least three times, the
vinyl ester polymer for analysis is produced by drying under
reduced pressure at 80.degree. C. for 3 days. This vinyl ester
polymer is dissolved in DMSO-D6, and subjected to the measurement
at 80.degree. C. by using proton NMR ("GX-500" available from JEOL
Ltd.) at 500 MHz. The proportion of the ethylene unit is calculated
by using the peaks derived from main-chain methine of the vinyl
ester (4.7 ppm to 5.2 ppm), and peaks derived from the main-chain
methylene of ethylene, the vinyl ester and the third component (0.8
ppm to 1.6 ppm).
Drilling Mud and Production Method Thereof
The drilling mud according to still another embodiment of the
present invention plays roles such as, for example: transporting
drilled clasts, drilling wastes and the like; improving lubricating
properties of bits and drill pipes; filling in holes on the porous
ground; balancing out the reservoir pressure that results from the
hydrostatic pressure (pressure from the rock stratum); and the
like. This drilling mud contains water and a muddy material as
principal components, and further contains the aforementioned
additive for a slurry as the additive for drilling mud slurry. The
drilling mud may also contain optional component(s) within a range
not leading to impairment of the effects of the present
invention.
Such a drilling mud may be produced by mixing the additive for a
slurry, a muddy material, and water. Specifically, the drilling mud
can be produced by adding the additive for a slurry, and as needed,
optional component(s), to as the base, a water-clay suspension
liquid prepared by dispersing and suspending the muddy material in
water.
Additive for Drilling Mud Slurry
The additive for a slurry as the additive for drilling mud slurry
contains the PVA powder described above. The particle size of the
additive for a slurry as the additive for drilling mud slurry is
preferably a size that enables passage through a sieve having a
nominal mesh opening size of 500 .mu.m (32 mesh). Since the PVA and
the PVA powder are as described above, the descriptions in this
paragraph are omitted.
However, it is necessary that the PVA powder contained in the
drilling mud has a particle size that enables passage through a
sieve having a nominal mesh opening size of 1.00 mm (16 mesh), and
the size that enables passage through a sieve having a nominal mesh
opening size of 500 .mu.m (32 mesh) is more preferred. When the PVA
powder contained in the drilling mud thus has the particle size
that enables passage through the sieve having a nominal mesh
opening size of 500 .mu.m (32 mesh), dehydration from the drilling
mud at high temperatures can be more inhibited. It is to be noted
that the lower limit of the particle size of the PVA powder is not
particularly limited as long as the particle size falls within the
range not leading to extremely high solubility, and is typically
the size not enabling passage through a sieve having a nominal mesh
opening size of 45 .mu.m (325 mesh), and preferably the size not
enabling passage through a sieve having a nominal mesh opening size
of 53 .mu.m (280 mesh).
The lower limit of the content of the PVA powder in the drilling
mud is preferably 0.5 kg/m.sup.3, and more preferably 3 kg/m.sup.3.
On the other hand, the upper limit of the content of the PVA powder
in the drilling mud is preferably 40 kg/m.sup.3, and more
preferably 30 kg/m.sup.3.
Muddy Material
Examples of the muddy material include bentonite, attapulgite,
sericite, a hydrous silicic acid magnesium salt and the like, and
of these, bentonite is preferred.
The lower limit of the amount of the muddy material blended in the
drilling mud is preferably 5 g, and more preferably 10 g with
respect to 1 kg of the water used in the drilling mud. On the other
hand, the upper limit of the amount of the muddy material blended
in the drilling mud is preferably 300 g, and more preferably 200 g
with respect to 1 kg of the water used in the drilling mud.
Optional Components
As the optional components, well-known additives may be used, and
for example, an aqueous solution of a copolymer of an
.alpha.-olefin having 2 to 12 carbon atoms with maleic anhydride,
or a derivative thereof (for example, maleic acid amide, maleic
acid imide), an alkali-neutralization product thereof, or the like;
a dispersant, a pH-adjusting agent, a defoaming agent, a thickening
agent, and the like may be included. The copolymer of an
.alpha.-olefin having 2 to 12 carbon atoms with maleic anhydride,
or a derivative thereof is exemplified by copolymers of an
.alpha.-olefin such as ethylene, propylene, butene-1, isobutene or
diisobutylene with maleic anhydride, or derivatives thereof (for
example, Kuraray Co., Ltd., "ISOBAM"). Further, the dispersant is
exemplified by a humic acid dispersant, a lignin dispersant and the
like, and of these, the lignin dispersant containing a sulfonic
acid salt is preferred.
Cement Slurry and Production Method Thereof
The cement slurry according to still other embodiment the present
invention is for use in: fixation of the casing pipe into the well;
and protection, etc., of the inner wall in the well by, being
injected into and hardened in, for example, tubular void portions
between the stratum and the casing pipe installed in the well. The
cement slurry contains the additive for a slurry as the additive
for a cement slurry, as well as a hardening powder and a liquid.
The cement slurry may contain optional component(s), within the
range not leading to impairment of the effects of the present
invention.
The cement slurry is produced by adding the additive for a slurry,
and the liquid and the hardening powder, as well as as needed,
optional component(s), and mixing using a stirrer or the like.
Additive for Cement Slurry
The additive for a slurry as the additive for a cement slurry
contains the PVA powder described above. The particle size of the
additive for a slurry as the additive for a cement slurry is
preferably the size that enables passage through a sieve having a
nominal mesh opening size of 250 .mu.m (60 mesh). Since the PVA and
the PVA powder are as described above, the descriptions in this
paragraph are omitted.
However, it is necessary that the PVA powder contained in the
cement slurry has a particle size that enables passage through a
sieve having a nominal mesh opening size of 1.00 mm (16 mesh), and
the size that enables passage through a sieve having a nominal mesh
opening size of 250 .mu.m (60 mesh) is preferred. When the PVA
powder contained in the cement slurry thus has the particle size
that enables passage through the sieve having a nominal mesh
opening size of 250 .mu.m (60 mesh), dehydration from the cement
slurry at high temperatures can be more inhibited. It is to be
noted that the lower limit of the particle size of the PVA powder
is not particularly limited as long as the particle size falls
within the range not leading to extremely high solubility, and the
particle size typically does not enable passage through a sieve
having a nominal mesh opening size of 45 .mu.m (325 mesh), and
preferably the particle size does not enable passage through a
sieve having a nominal mesh opening size of 53 .mu.m (280
mesh).
The lower limit of the content of the PVA powder in the cement
slurry is preferably 0.1% (BWOC), and more preferably 0.2% (BWOC).
On the other hand, the upper limit of the content of the PVA powder
in the cement slurry is preferably 2.0% (BWOC), and more preferably
1.0% (BWOC). It is to be noted that "BWOC" means "By Weight Of
Cement" which is indicated on mass basis of the cement.
Hardening Powder
The hardening powder is exemplified by Portland cement, mixed
cement, eco-cement, special cement and the like. Moreover, the
hardening powder is preferably water-hardening cement which is
solidified through a reaction with water. It is to be noted that
when the cement slurry is used for drilling, geothermal-well cement
and oil-well cement are preferred.
The Portland cement is exemplified by those defined according to
JIS-R5210: 2009, and specific examples include ordinary Portland
cement, high-early-strength Portland cement, ultra
high-early-strength Portland cement, moderate heat Portland cement,
low-heat Portland cement, sulfate resisting Portland cement,
low-alkali Portland cement, and the like.
The mixed cement is exemplified by those defined according to
JIS-R5211 to 5213: 2009, and specific examples include
blast-furnace slag cement, fly ash cement, silica cement, and the
like.
The special cement may include those prepared using the Portland
cement as a base, those prepared by changing the component and/or
the particle grade constitution of the Portland cement, and those
containing components differing from the Portland cement.
The special cement prepared using the Portland cement as a base is
exemplified by distensible cement, low heat cement of a
two-component system, low heat cement of a three-component system,
and the like.
The special cement prepared by changing the component and/or the
particle grade constitution of the Portland cement is exemplified
by white Portland cement, a cement type hardening material
(geocement), ultrafine particle cement, high-belite type cement,
and the like.
The special cement containing components differing from the
Portland cement is exemplified by rapid hardening cement, alumina
cement, phosphate cement, non-hydraulic cement, and the like.
Liquid
The liquid may be selected depending on the type of the hardening
powder, and is exemplified by water, a solvent, and a mixture of
the same. In general, water is used.
The ratio of the hardening powder to the liquid in the cement
slurry may be appropriately predetermined depending on the specific
gravity of the intended slurry as well as the strength of the
hardened product, etc. For example, when the drilling cement slurry
is constituted as a cement slurry for drilling with the
water-hardening cement, the ratio (W/C) of water to cement is
preferably 25 weight %, and more preferably 30 weight %, from the
viewpoints of the specific gravity of the slurry, as well as the
strength of the hardened product, and the like. The upper limit of
the ratio W/C is preferably 100 weight %, and more preferably 80
weight %, from the viewpoints of the specific gravity of the
slurry, as well as the strength of the hardened product, and the
like.
Optional Components
As the optional component, a dispersant, a retardant and/or a
defoaming agent may be contained in the cement slurry, and
additive(s) other than these may be also contained.
Dispersant
The dispersant is exemplified by a naphthalenesulfonic
acid-formalin condensate, a melaminesulfonic acid-formalin
condensate, an anionic macromolecule such as a polycarboxylic acid
polymer and the like, and of these, naphthalenesulfonic
acid-formalin condensate is preferred. The lower limit of the
content of the dispersant in the cement slurry is typically 0.05%
(BWOC), and preferably 0.2% (BWOC). On the other hand, the upper
limit of the content of the dispersant in the cement slurry is and
2% (BWOC), and preferably 1% (BWOC).
Retardant
The retardant is exemplified by oxycarboxylic acid and salts
thereof, saccharides such as monosaccharides and polysaccharides,
and the like, and of these, the saccharides are preferred. The
lower limit of the content of the retardant in the cement slurry is
typically 0.005% (BWOC), and preferably 0.02% (BWOC). On the other
hand, the upper limit of the content of the retardant in the cement
slurry is 1% (BWOC), and preferably 0.3% (BWOC).
Defoaming Agent
The defoaming agent is exemplified by an alcohol alkylene oxide
adduct, a fatty acid alkylene oxide adduct, polypropylene glycol, a
fatty acid soap, a silicone compound and the like, and of these, a
silicone compound is preferred. The lower limit of the content of
the defoaming agent in the cement slurry is typically 0.0001%
(BWOC), and preferably 0.001% (BWOC). On the other hand, the upper
limit of the content of the defoaming agent in the cement slurry is
0.1% (BWOC), and preferably 0.05% (BWOC).
Additives
Taking into consideration the intended use, the composition and the
like, the cement slurry may contain additives such as, e.g., a
cement accelerator, a low-density additive, a high-density
additive, a foaming agent, a crack preventive agent, a bubbling
agent, an AE agent, a cement-distensible agent, a cement strength
stabilizer, a fine aggregate such as a silica powder, a silica
fume, a fly ash, a limestone powder and a crushed sand, a coarse
aggregate such as a crushed stone, a hollow balloon and the like.
Further, these additives may be used alone of one type, or two or
more types thereof may be used in combination.
EXAMPLES
Hereinafter, the present invention will be described by way of
Examples and Comparative Examples, but the present invention is not
in any how limited to the following Examples.
Preparation Example 1: Preparation of Dry PVA (PVA-1)
Into a 250-L reaction vessel equipped with a stirrer, a
nitrogen-feeding port, an ethylene-feeding port, an initiator
addition port and a delay solution addition port were charged 127.5
kg of vinyl acetate and 22.5 kg of methanol, and the temperature of
the mixture was elevated to 60.degree. C. Thereafter, nitrogen was
bubbled for 30 min to replace inside the system by nitrogen. Then,
ethylene was introduced such that the pressure in the reaction
vessel became 4.9 Kg/cm.sup.2. As the initiator, a reaction
initiator solution was prepared by dissolving
2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (AMV) in methanol
to the concentration of 2.8 g/L, and a nitrogen gas was bubbled
into this reaction initiator solution to replace inside the system
by nitrogen, and this solution was employed as the initiator
solution. This initiator solution in a volume of 45 mL was
introduced into the reaction vessel regulated to 60.degree. C.,
whereby the polymerization was initiated. During the
polymerization, ethylene was introduced to maintain the pressure in
the reaction vessel of 4.9 Kg/cm.sup.2, whereas the polymerization
temperature was maintained at 60.degree. C., and the initiator
solution was continuously added to the reaction vessel at 143 mL/hr
to carry out the polymerization. Four hrs later, when the
conversion (rate of polymerization) became 40%, the reaction vessel
was cooled to stop the polymerization. Furthermore, the reaction
vessel was opened to remove ethylene, and nitrogen gas was bubbled
so as to completely remove ethylene. Subsequently, the unreacted
vinyl acetate monomer was removed under a reduced pressure to give
a methanol solution of polyvinyl acetate. To this polyvinyl acetate
solution was added methanol to adjust the concentration of
polyvinyl acetate to 25% by mass. Furthermore, to 400 g of the
methanol solution of polyvinyl acetate (polyvinyl acetate in the
solution: 100 g) was added 23.3 g of an alkali solution (10% by
mass methanol solution of NaOH; molar ratio of NaOH to the vinyl
acetate unit in polyvinyl acetate being 0.1) to carry out
saponification. About one min later after adding the alkali
solution, the gelated matter was ground by a grinder, and the
mixture was left to stand at 40.degree. C. for 1 hr, thereby
allowing the saponification to proceed. Thereafter, 1,000 g of
methyl acetate was added thereto, and the mixture was left to stand
at room temperature for 30 min. To the white solid (PVA) obtained
by filtration was added 1,000 g of methanol and the mixture was
left to stand for 3 hrs at room temperature to permit washing.
Then, PVA obtained by deliquoring through centrifugation was left
to stand in a dryer at 100.degree. C. for 3 hrs to give dry PVA
(PVA-1).
Characterization of PVA
With respect to the dry PVA (PVA-1), the degree of saponification,
the average degree of polymerization, the amount of 1,2-glycol
linkage, and the proportion of the ethylene unit were each analyzed
according to the following procedure.
Degree of Saponification
The degree of saponification of the dry PVA (PVA-1) was 99.5 mol %
as determined according to JIS-K6726: 1994.
Average Degree of Polymerization
After the polymerization in Preparation Example 1, using the
methanol solution of polyvinyl acetate obtained through removing
the unreacted vinyl acetate monomer, saponification was carried out
with the molar ratio of the alkali of 0.5 and then the product was
ground, followed by being left to stand at 60.degree. C. for 5 hrs
to allow the saponification to proceed. Thereafter, a methanol
Soxhlet procedure was performed for 3 days, and then drying under
reduced pressure carried out at 80.degree. C. for 3 days gave a
purified PVA. This purified PVA has the average degree of
polymerization as determined according to JIS-K6726: 1994 of
1,720.
Amount of 1,2-Glycol Linkage
The purified PVA thus prepared in order to determine the average
degree of polymerization was dissolved in DMSO-D6, and the amount
of 1,2-glycol linkage was determined to be 1.6 mol % as measured at
80.degree. C. using proton NMR ("GX-500" available from JEOL Ltd.)
at 500 MHz.
Proportion of Ethylene Unit
After the polymerization in Preparation Example 1, the methanol
solution of polyvinyl acetate obtained through removing the
unreacted vinyl acetate monomer was subjected to purification by
reprecipitation three times including precipitation in n-hexane and
dissolving in acetone. Then, drying under reduced pressure at
80.degree. C. for 3 days gave purified polyvinyl acetate. This
purified polyvinyl acetate was dissolved in DMSO-D6, and the
proportion of ethylene unit (i.e., ethylene content) was determined
to be 5 mol % as measured at 80.degree. C. by using proton NMR
("GX-500" available from JEOL Ltd.) at 500 MHz.
Preparation Examples 2 to 17: Preparation of Dry PVAs (PVA-2) to
(PVA-17)
In a similar manner to Preparation Example 1, dry PVA (PVA-2) to
(PVA-17) having characteristics shown in Table 1 were prepared.
TABLE-US-00001 TABLE 1 Characteristics of vinyl alcohol polymer
(PVA) degree of amount of 1,2- saponification average degree of
glycol ethylene (mol %) polymerization linkage (mol %) content (mol
%) Preparation Example 1 PVA-1 99.5 1,720 1.6 5.0 Preparation
Example 2 PVA-2 99.9 1,720 1.6 5.0 Preparation Example 3 PVA-3 99.9
1,770 1.3 5.0 Preparation Example 4 PVA-4 99.7 1,600 1.6 7.0
Preparation Example 5 PVA-5 99.5 2,450 1.6 3.0 Preparation Example
6 PVA-6 99.9 2,450 1.6 3.0 Preparation Example 7 PVA-7 99.9 2,430
1.6 0.0 Preparation Example 8 PVA-8 99.9 2,520 1.4 0.0 Preparation
Example 9 PVA-9 99.9 3,450 1.6 0.0 Preparation Example 10 PVA-10
88.2 2,430 1.6 0.0 Preparation Example 11 PVA-11 98.5 2,430 1.6 0.0
Preparation Example 12 PVA-12 98.5 1,720 1.6 5.0 Preparation
Example 13 PVA-13 99.3 2,430 1.6 0.0 Preparation Example 14 PVA-14
99.3 2,470 1.6 3.0 Preparation Example 15 PVA-15 99.9 1,700 2.0 2.0
Preparation Example 16 PVA-16 99.9 1,260 1.6 0.0 Preparation
Example 17 PVA-17 99.9 1,260 1.6 5.0
Example 1: Preparation of Drilling Mud
Into a cup of Hamilton Beach Mixer was weighed 300 g of ion
exchanged water, and thereto was added 6 g of bentonite (available
from TELNITE CO., LTD., "TELGEL E"). After the mixture was
sufficiently stirred, the mixture was left to stand for 24 hrs in
order to allow bentonite to be sufficiently swollen. In the
meantime, the dry PVA (PVA-1) was subjected to a sieve having a
nominal mesh opening size of 1.00 mm (16 mesh), and 1.5 g of the
dry PVA (PVA-1) powder passed through the sieve was collected. This
powder was added as an additive for a drilling mud to the
dispersion liquid of bentonite to give a drilling mud (D-1).
Examples 2 to 9, and Comparative Examples 1 to 8
Drilling muds (D-2) to (D-9) and (d-1) to (d-8) were prepared in a
similar manner to Example 1 except that dry PVA (PVA-2) to (PVA-17)
powders were each used as shown in Table 2.
Example 10
A drilling mud (D-10) was prepared in a similar manner to Example 6
except that the dry PVA (PVA-6) was subjected to a sieve having a
nominal mesh opening size of 500 .mu.m (32 mesh), and the powder of
the dry PVA (PVA-6) passed through the sieve was used.
Example 11
A drilling mud (D-11) was prepared in a similar manner to Example 7
except that the dry PVA (PVA-7) was subjected to a sieve having a
nominal mesh opening size of 500 .mu.m (32 mesh), and the dry PVA
(PVA-7) powder passed through the sieve was used.
Comparative Example 9
After the dry PVA (PVA-1) was mixed with water and the mixture was
thoroughly stirred, undissolved PVA powder was removed by using
wire mesh having a nominal mesh opening size of 75 .mu.m (200 mesh)
to give an aqueous PVA solution having the PVA concentration of 4%
by weight. This PVA solution in an amount of 37.5 g was added to a
dispersion liquid of bentonite prepared using 264 g of ion
exchanged water and 6 g of bentonite in a similar manner to Example
1, whereby a drilling mud (d-9) was prepared.
Comparative Example 10
A drilling mud (d-10) was prepared in a similar manner to Example 1
except that the dry PVA (PVA-1) was subjected to a sieve having a
nominal mesh opening size of 1.00 mm (16 mesh), and the dry PVA
(PVA-1) powder not having passed through the sieve was used.
Evaluations
The drilling muds (D-1) to (D-11) and (d-1) to (d-10) of Examples 1
to 11 and Comparative Examples 1 to 10 were evaluated with respect
to the viscosity and the amount of dehydration each according to
the following procedure. In addition, the solubility of sieved
powders of dry PVAs (PVA-1) to (PVA-17) used for the preparation of
these drilling muds (D-1) to (D-11) and (d-1) to (d-10) was
determined according to the following procedure. The results of the
evaluations are shown in Table 2.
Solubility
Into a 300-mL beaker previously charged with 100 g of water at
60.degree. C. was charged 4 g of dry PVA powder, and the mixture
was stirred under a condition with the rotation frequency of 280
rpm at 60.degree. C. for 3 hrs by using a magnetic stirrer with a
bar in the length of 3 cm while preventing evaporation of water.
Then, undissolved powder was separated by using a wire mesh having
a nominal mesh opening size of 75 .mu.m (200 mesh). The undissolved
PVA powder was dried in a heating dryer at 105.degree. C. for 3
hrs, and thereafter the weight was measured. The solubility of the
dry PVA powder was determined from the weight of the undissolved
PVA powder, and the weight of the dry PVA powder which was charged
into the beaker (4 g). However, the solubility was not determined
on Comparative Example 9 since PVA-1 was added in the form of an
aqueous solution.
Viscosity
The viscosity of the drilling mud was measured by using a B type
viscometer at 25.degree. C., 30 rpm, and the value obtained after
10 sec was employed. A smaller value of the viscosity of the
drilling mud indicates a more favorable feature, and the evaluation
may be made to be: "favorable" in the vase of being 18 mPas or
less; and "unfavorable" in the case of exceeding 18 mPas.
Amount of Dehydration
The measurement of the amount of dehydration of the drilling mud
was carried out by using "HPHT Filter Press Series 387" available
from Fann Instrument company, after the drilling mud was charged
into the cell in which the temperature had been adjusted to
150.degree. C. and was left to stand for 3 hrs. In the measurement,
the pressure was applied from both the above and below the cell
such that the differential pressure therebetween was 500 psi. A
smaller value of the amount of dehydration of the drilling mud
indicates a more favorable feature, and the evaluation may be made
to be: "favorable" in the case of being 30 ml or less; and
"unfavorable" in the case of exceeding 30 ml.
TABLE-US-00002 TABLE 2 Additive for drilling mud Drilling mud
solubility drilling mud viscosity amount of PVA type particle size*
(%) type (mPa s) dehydration(mL) Example 1 PVA-1 1.00 mm passed
17.4 D-1 10 23 Example 2 PVA-2 1.00 mm passed 15.0 D-2 10 15
Example 3 PVA-3 1.00 mm passed 14.2 D-3 10 13 Example 4 PVA-4 1.00
mm passed 15.8 D-4 10 14 Example 5 PVA-5 1.00 mm passed 18.0 D-5 10
20 Example 6 PVA-6 1.00 mm passed 16.2 D-6 10 12 Example 7 PVA-7
1.00 mm passed 18.0 D-7 10 25 Example 8 PVA-8 1.00 mm passed 17.8
D-8 10 22 Example 9 PVA-9 1.00 mm passed 15.4 D-9 10 15 Example 10
PVA-6 500 .mu.m passed 17.3 D-10 12 7 Example 11 PVA-7 500 .mu.m
passed 20.1 D-11 14 20 Comparative Example 1 PVA-10 1.00 mm passed
100 d-1 350 >100 Comparative Example 2 PVA-11 1.00 mm passed
55.0 d-2 21 >100 Comparative Example 3 PVA-12 1.00 mm passed
58.0 d-3 19 >100 Comparative Example 4 PVA-13 1.00 mm passed
34.8 d-4 14 42 Comparative Example 5 PVA-14 1.00 mm passed 31.0 d-5
12 38 Comparative Example 6 PVA-15 1.00 mm passed 26.9 d-6 11 32
Comparative Example 7 PVA-16 1.00 mm passed 30.2 d-7 11 50
Comparative Example 8 PVA-17 1.00 mm passed 29.5 d-8 11 46
Comparative Example 9 PVA-1 added as an aqueous solution d-9 1200
>100 Comparative Example 10 PVA-1 1.00 mm not passed 16.8 d-10
10 90 *The dimension is the nominal mesh opening size defined in
"JIS Z8801:2000".
As is clear from the results shown in Table 2, the drilling muds
(D-1) to (D-11) of Examples 1 to 11 had a low viscosity, and the
amount of dehydration at 150.degree. C. was 25 mL or less. Thus,
dehydration at a high temperature was significantly inhibited to a
very low level.
On the other hand, any of the solubility of the drilling muds (d-1)
to (d-5) of Comparative Examples 1 to 5 was greater than 25%, and
consequently the amount of dehydration of the drilling mud at
150.degree. C. exceeded 30 mL, indicating the failure of sufficient
inhibition of the dehydration at a high temperature, which may
result from the use of the dry PVA having the degree of
saponification of less than 99.5 mol % in the drilling muds (d-1)
to (d-5).
The solubility of the drilling mud (d-6) of Comparative Example 6
was greater than 25%, and consequently the amount of dehydration of
the drilling mud at 150.degree. C. was 32 mL, indicating the
failure of sufficient inhibition of the dehydration at a high
temperature, which may result from the use of the dry PVA having
the amount of 1,2-glycol linkage of greater than 1.8 mol %.
The solubility of the drilling muds (d-7) and (d-8) of Comparative
Examples 7 and 8 was greater than 25%, and further the amount of
dehydration of the drilling mud at 150.degree. C. was at least 35
mL, indicating the failure of sufficient inhibition of the
dehydration at a high temperature, which may result from the use of
the dry PVA having the average degree of polymerization of less
than 1,500.
Although the dry PVA (PVA-1) was used in the drilling mud (d-9) of
Comparative Example 9 similarly to Example 1, the viscosity of the
drilling mud (d-9) was very high, and further the amount of
dehydration of the drilling mud at 150.degree. C. was greater than
100 mL, indicating markedly insufficient inhibition of the
dehydration at a high temperature, which may result from the
addition of the dry PVA (PVA-1) after dissolving in water
beforehand.
Although the dry PVA (PVA-1) was used in the drilling mud (d-10) of
Comparative Example 10 similarly to Example 1, the solubility at
60.degree. C. was somewhat low; however, the amount of dehydration
of the drilling mud at 150.degree. C. was 90 mL, indicating
markedly insufficient inhibition of the dehydration at a high
temperature, which may result from the great particle size when
added to the drilling mud (d-10) that does not enable the passage
through the nominal mesh opening size of 100 mm (16 mesh).
From the results described above, when used in preparation of the
drilling mud, the powdery vinyl alcohol polymer having: the
solubility of 25% or less when immersed in hot water at 60.degree.
C. for 3 hrs; the degree of saponification of at least 99.5 mol %;
the average degree of polymerization of at least 1,500 and 4,500 or
less; and the amount of the 1,2-glycol linkage of 1.8 mol % or
less, and is capable of passing through a sieve having a nominal
mesh opening size of 100 mm (16 mesh), was able to lower the
viscosity of the drilling mud and to inhibit the dehydration at a
high temperature, verifying that the powdery vinyl alcohol polymer
was very useful as the additive for a drilling mud.
Example 12
Preparation of Cement Slurry
A cement slurry (S-1) was prepared by charging into a juice mixer,
4 g of the dry PVA (PVA-6) powder as an additive for a cement
slurry, passed through a sieve having a nominal mesh opening size
of 250 .mu.m (60 mesh) obtained by subjecting the dry PVA (PVA-6)
to sieving, 320 g of ion exchanged water, 800 g of class H cement
for wells, 4 g of naphthalenesulfonic acid-formalin condensate
sodium salt (Dipersity Technologies Inc., "Daxad-19") and 0.16 g of
lignosulfonic acid sodium salt (Lignotech USA, Inc., "Keling 32L"),
and then mixing with stirring. It is to be noted that the amount of
the dry PVA (PVA-6) powder added was 0.5% on mass basis of the
cement (BWOC).
Example 13
A cement slurry (S-2) was prepared in a similar manner to Example
12 except that the dry PVA (PVA-9) was used.
Comparative Example 11
A cement slurry (s-1) was prepared in a similar manner to Example
12 except that the dry PVA (PVA-10) was used.
Comparative Example 12
A cement slurry (s-2) was prepared in a similar manner to
Comparative Example 11 except that the amount of the dry PVA
(PVA-10) added was changed to 0.8% (BWOC).
Comparative Example 13
A cement slurry (s-3) was prepared in a similar manner to Example
12 except that the dry PVA (PVA-13) was subjected to a sieve having
a nominal mesh opening size of 180 .mu.m (80 mesh), and the dry PVA
(PVA-13) powder passed through the sieve was used.
Evaluations
The cement slurries (S-1), (S-2) and (s-1) to (s-3) of Examples 12
and 13, and Comparative Examples 11 to 13 were evaluated with
respect to the viscous characteristic and the amount of dehydration
each according to the following procedure. The results of the
evaluations are shown in Table 3. In addition, the solubility of
powders of the dry PVAs (PVA-6), (PVA-9), (PVA-10) and (PVA-13)
used for the preparation of these cement slurries (S-1), (S-2) and
(s-1) to (s-3) obtained after the sieving is shown in Table 3.
Viscosity
The viscosities of the cement slurries were evaluated in terms of
plastic viscous characteristic (PV) and yield value (YV). The
plastic viscous characteristic (PV) is a value of flow resistance
generated by mechanical friction of solid contents included in the
cement slurry. The yield value (YV) is a shearing force required
for continuing flowing when a fluid is in a flowing state, and is a
flow resistance generated by a tractive force among solid particles
included in the cement slurry.
The plastic viscosity (PV) and the yield value (YV) were measured
according to the method described in "Appendix H" of "API10"
(American Institute Specification 10), after adjusting the
temperature of the cement slurry to 25.degree. C. or 90.degree. C.
A smaller value of the plastic viscosity (PV) of the cement slurry
indicates a more favorable feature, and may be evaluated to be:
"favorable" in the case of being 60 cp or less; and "unfavorable"
in the case of exceeding 60 cp under the condition of 20.degree. C.
Further, the yield value (YV) of the cement slurry may be evaluated
to be: "favorable" in the case of being 7 lb/100 ft.sup.2 or less;
and "unfavorable" in the case of exceeding 7 lb/100 ft.sup.2 under
the condition of 20.degree. C. It is to be noted that the plastic
viscous characteristic (PV) and the yield value (YV) were each
calculated in accordance with the following formula: plastic
viscous characteristic (PV)=[(reading at 300 rpm)-(reading at 100
rpm)].times.1.5; yield value (YV)=[(reading at 300 rpm)-(plastic
viscous characteristic)].
Amount of Dehydration
The amount of dehydration of the cement slurry was measured
according to the method described in "Appendix H" of "API10"
(American Institute Specification 10), in terms of the amount
dehydrated from the cement slurry having the temperature adjusted
to 90.degree. C. for 30 min, under a condition of the differential
pressure of 1,000 psi. A smaller value of the amount of dehydration
of the cement slurry indicates a more favorable feature, and the
evaluation may be made to be: "favorable" in the case of being 35
ml or less; and "unfavorable" in the case of exceeding 35 ml.
TABLE-US-00003 TABLE 3 Cement slurry Additive for cement slurry
cement amount of viscous characteristic amount of solubility slurry
added PVA PV YV dehydration PVA type particle size*.sup.1 (%) type
(% by mass)*.sup.2 (cp) (lb/100 ft.sup.2) (mL) Example 12 PVA-6 250
.mu.m passed 17.8 S-1 0.5 32 (20.degree. C.) 2 (20.degree. C.) 25
48 (90.degree. C.) 9 (90.degree. C.) Example 13 PVA -9 250 .mu.m
passed 15.8 S-2 0.5 35 (20.degree. C.) 3 (20.degree. C.) 32 54
(90.degree. C.) 10 (20.degree. C.) Comparative PVA-10 250 .mu.m
passed 100 s-1 0.5 86 (20.degree. C.) 11 (20.degree. C.) 313
Example 11 36 (90.degree. C.) 8 (90.degree. C.) Comparative PVA-10
250 .mu.m passed 100 s-2 0.8 132 (20.degree. C.) 28 (20.degree. C.)
36 Example 12 58 (90.degree. C.) 5 (90.degree. C.) Comparative
PVA-13 180 .mu.m passed 35.2 s-3 0.5 35 (20.degree. C.) 1
(20.degree. C.) 340 Example 13 42 (90.degree. C.) 10 (90.degree.
C.) *.sup.1The dimension is the nominal mesh opening size defined
in "JIS-Z8801:2000". *.sup.2By Weight Of Cement (BWOC)
As is clear from the results shown in Table 3, the cement slurries
(S-1) and (S-2) of Examples 12 and 13 had a low viscosity, and the
amounts of dehydration at 90.degree. C. were 25 mL and 32 mL,
respectively, indicating inhibited dehydration at a high
temperature.
On the other hand, the solubility of the cement slurry (s-1) of
Comparative Example 11 was greater than was greater than 25%, and
consequently the amount of dehydration of the cement slurry at
90.degree. C. was 313 mL, indicating the failure of sufficient
inhibition of the dehydration at high temperatures in the amount of
addition which is identical to that of the cement slurries of
Examples 12 and 13, which may result from the use of the dry PVA
(PVA-10) which was partially saponified to the degree of
saponification of 88.2 mol %.
Although the dry PVA (PVA-10) partially saponified identical to the
cement slurry of Comparative Example 11 was used in the cement
slurry (s-2) of Comparative Example 12, the amount of dehydration
of the cement slurry at 90.degree. C. was significantly improved to
be 36 mL, which may result from the high amount of addition of 0.8
(% BWOC). However, PV at 20.degree. C. was as high as 132 cp
revealing the results not suited for practical applications, which
may result from the high amount of addition of the dry PVA
(PVA-10).
The amount of dehydration of the cement slurry at 90.degree. C. of
the cement slurry (s-3) of Comparative Example 13 was 340 mL, which
may result from the use of the dry PVA (PVA-13) having the degree
of saponification of 99.3 mol %, indicating the failure of
sufficient inhibition of the dehydration at high temperatures.
From the results described above, when used in preparation of the
drilling mud and the cement slurry, the powdery vinyl alcohol
polymer having: the solubility of 25% or less when immersed in hot
water at 60.degree. C. for 3 hrs; the degree of saponification of
at least 99.5 mol %; the average degree of polymerization of at
least 1,500 and 4,500 or less; and the amount of 1,2-glycol linkage
of 1.8 mol % or less, and is capable of passing through a sieve of
250 .mu.m (60 mesh), exhibited inhibition of the dehydration and
viscosity elevation at a high temperature even if used in a smaller
amount, verifying that the powdery vinyl alcohol polymer was very
useful as the additive for a drilling mud and a cement slurry.
INDUSTRIAL APPLICABILITY
According to the present invention, an additive for a slurry, a
drilling mud and a drilling cement slurry are provided which are
capable of inhibiting viscosity elevation and dehydration at high
temperatures at low cost, through use for a slurry for civil
engineering and construction (for example, a drilling mud and a
drilling cement slurry for use in well drilling. etc.), and the
like.
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